1. Make the Ganache Filling:

1. In a heatproof bowl, add the semi-sweet chocolate chips.
2. Heat the heavy cream until steaming (but not boiling) and pour it over the chocolate.
3. Let sit for 1-2 minutes, then stir until smooth.
4. Refrigerate for about 30 minutes until firm enough to scoop.

2. Prepare the Cookie Dough:

1. In a mixing bowl, cream together butter, brown sugar, and granulated sugar until light and fluffy.
2. Add egg yolks and vanilla extract, then mix until smooth.
3. Sift in the flour, cocoa powder, baking powder, and salt. Mix until a soft dough forms.

3. Assemble the Cookies:

1. Scoop about 1 ½ tablespoons of dough and flatten it in your palm.
2. Place a small scoop (about 1 teaspoon) of chilled ganache in the center.
3. Wrap the dough around the ganache, sealing the edges, and roll into a ball.
4. Repeat with the remaining dough and ganache.

4. Bake:

1. Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
2. Place cookies 2 inches apart on the prepared sheet.
3. Bake for 10-12 minutes until set around the edges but slightly soft in the center.
4. Allow to cool for 5 minutes on the tray, then transfer to a wire rack.

5. Serve:

• Dust with powdered sugar before serving.
• Enjoy warm for the best gooey lava effect!